Diagnosis. An elongate, bilobate furrow that can vary in depth with respect to the bedding plane, may be straight and/or gently curved (not tightly or sharply) within or upon the bedding surface, and may be composed of repetitive sets (or series) of imprints (ridges) along its length (though in most cases these ridges cannot be differentiated into distinctive set patterns); ridges in central part of furrow usually aligned in a herringbone shape and more or less continuous along length of furrow; also, sometimes, outside herringbone-aligned ridges, the trace may exhibit pair of narrow, comparatively smooth outer zones with or without fine brush-like impressions, and additionally there may be presence of lateral ridges.
Diagnosis: Elongate (length:width ratio >2:1), typically ribbon-like, bilobate (rarely unilobate) interface burrows or trails preserved as furrows with median ridgesmwhen preserved in concave epirelief (or bilobate trails with median groove when preserved in counterpart convex hyporelief), or paired furrows that are in close proximity (less than the width of a furrow apart). Furrows covered by herring-bone-shaped or transverse striations, with or without smooth or longitudinally striate zones peripheral to the inner striations, with or without outer lateral ridges and/or wisplike markings if preserved on bedding soles (after Fillion and Pickerill, 1990)